The present invention relates to a continuous treating apparatus for heating and denitrating a nitrate solution such as a solution of plutonium nitrate, uranyl nitrate, a mixture thereof or the like and converting the nitrate solution to oxide powder. More particularly, the present invention relates to an apparatus for heating and denitrating continuously and efficiently the nitrate solution of nuclear fuel materials by microwaves.
Methods and apparatus of various systems have been developed heretofore for heating and denitrating the nitrate solution of nuclear fuel materials, such as a solution of plutonium nitrate, uranyl nitrate, a mixture thereof, or the like, recovered by reprocessing of spent nuclear fuels and for converting it to a denitrated product composed of oxides by using microwaves. As a continuous treating apparatus in particular, a screw-type apparatus (e.g. Japanese Patent Publication No. 22554/1988) and a turn table-type apparatus using a plurality of vessels (e.g. Japanese Patent Laid-Open No. 79394/1987) have been proposed.
The advantage of the method which converts the nitrate solution to the denitrated product by heating and denitrating the nitrate solution by microwaves is that the resulting denitrated product becomes a porous foamed body because the material to be treated is heated from inside by microwaves.
However, the denitrated product produced actually by using the above-described conventional continuous treating apparatus is in most cases hard and mass-like and is not entirely satisfactory from the aspects of handlability of the product and dischargeability from the apparatus. The maintenance and inspection properties of the prior art apparatus is also not satisfactory.